This invention relates to an improved system and method for restraining cargo during transportation. More particularly, this invention relates to a novel system and method for securing and restraining undesired movement of cargo such as drums, boxes, rigid and flexible containers—palletized or not palletized—within the interior of an overland transport container such as a truck body, a truck trailer, railroad box car or the like.
Overland transport containers are often loaded with cargo in containment enclosures such as fifty five gallon closed head drums, super sacks or plastic reinforced bags, plastic wrapped bundles or cased goods. Moreover overland cargo can include non-contained metal coils, specialty heavy paper rolls, plastic or metal containers mounted on pallets, boxes, plastic wrapped pallets and the like. Although each containment enclosure or bundle may be quite heavy and stationary at rest, the mass of a transport load can produce considerable momentum force as overland cargo is placed in motion. In this regard trucks are subject to stopping and starting forces, emergency braking, bumps and swaying from uneven road beds, centrifugal forces on curves, vibration, etc., which tend to shift loads.
In addition to being pulled by truck tractors over highways, overland route containers are often positioned on railroad flat cars or cargo is loaded directly in box cars. Rail cars may be made up by a coupling or humping process within a switching yard. When a railroad car is rolled into a stationary string of cars, the impact causes the car couplings to lock together with a jolt. This impact can apply a significant impulse force to cargo within or upon the rail car. Moreover, during transport, railway cars are subject to braking forces, run-in and run-out coupler impacts over grades, rail vibration, dips in the track, and swaying.
Each of these overland forces has the potential to impart a substantial force onto cargo within an overland container. In this, when an overland container changes direction or speed, cargo within the container tends to continue along the previously existing path until it contacts an interior wall of the container. Without some type of restraint and/or cushioning system, the cargo builds up considerable momentum, independent of the container. The amount of momentum is equal to the mass of a load multiplied by its velocity. Accordingly it will be appreciated that in the case of large cargo loads, even a small change in velocity or direction can generate substantial forces.
When cargo contacts the interior walls or doors of a transport container, the force necessary to reduce its momentum to zero must be absorbed by the goods and/or the container. Such forces can result in damage to the cargo, damage to the interior walls or doors of the container, damage to the cargo packing, and may create dangerous leaks if the cargo is a hazardous material. Accordingly, it is undesirable to permit cargo to gain any momentum independent of a container during transport. This is accomplished by restraining the cargo within the container so that the cargo and the container are essentially united and operationally function as one object during transport.
In order to secure cargo during transport and minimize undesired shifting and damage load containment enclosures are often secured to the floor and/or sides of the trailer or boxcar by specially fabricated wood framing, floor blocking, rubber mats, steel strapping, heavy air bags, etc. Each of these previously known systems for securement has limitations associated with construction cost, lack of strength sufficient to secure heavy loads, etc. Moreover, although rear doors of a trailer may be relied on to at least partially secure non-hazardous materials such as food-stuffs, tissue or soft paper products, furniture, appliances, etc., for hazardous materials, and many other types of loads, the rear doors of a container may not be used to even partially secure a load. In fact, in order to comply with Department of Transportation Regulations and Bureau of Explosives, hazardous materials are not even permitted to come in contact with rear doors during an impact.
Still further, in some instances a trailer or boxcar may be used for shipping where only a partial load is carried. A partial load might be positioned within a center location of a trailer. In this instance it may be impractical to construct wooden front and rear dunnage sufficient to secure a load where the front of the trailer is not utilized.
In the past, various dunnage materials have been utilized within overland containers to eliminate unwanted movement or shifting of a load during transport. The drums, boxes, or other containers have been restrained in several different ways. Primarily, cargo was stabilized by a method of load-locking and lumber bracing. This system involves strategically placing lumber between a load face and the rear doors of a transport container. This, however, can be a costly, time consuming, and generally inefficient means of securing a load. In this, the blocking process requires carpenters and is often outsourced to contractors. Moreover, wooden barriers can be time consuming to install. Further wood bracing can be somewhat brittle and subject to failure as a result of an abrupt impact.
When wood bracing is utilized as a system of restraint, because of the bracing system bulk, shippers may be forced to ship containers that are not filled to capacity. This reduces transport efficiency and increases transportation costs. Moreover, some types of wood, such as conifer woods, are not acceptable to cross international boundaries without certification of special fumigation or heat treatment processing of conifer wood dunnage.
Other known means of restraint such as ropes, metal or plastic straps or stands and the like appearing in the past have tended to exhibit impaired performance and are often not functionally suitable to restrain loads under even moderate conditions. Consequently, a need exists for securing lading in truck trailers, boxcars, and other overland containers that is functionally effective, cost-efficient, labor-efficient, and able to comply with Department of Transportation and Bureau of Explosives regulations. Still further a need exists for securement systems that have an enhanced means of application to facilitate cost and efficient use of relatively unskilled labor for loading operations.
In addition to the above, other restraining systems known in the past required multiple elements and equipment which were cumbersome to store, were arduous to install, and often required a degree of skilled labor. Systems using straps, nails, anchors, bolts, or other tools all require substantial storage space even when not in use. Furthermore, such systems increase the safety risk to the workers restraining the cargo. Still further such systems have often been unable to satisfy safety and travel limits imposed by regulatory bodies in various countries.
In addition to the above concerns, systems and procedures used in the past relying on accessories located within the cargo container were often not able to secure a partial load. That is, if the load does not extend to the front or rear of the container, such as a centrally located load, the necessary anchors may not be available in an area where they can be effectively used.
At least one method and apparatus for restraining cargo movement which overcomes some of the foregoing limitations is disclosed in U.S. Pat. No. 4,264,251, of common assignment with the subject application. The invention disclosed in that patent comprises sealing strips that are adhered to opposing sidewalls of a container, a strip of bracing material, and a joining mechanism is used to bind the ends of the strips together into a secure and taut restraint.
In the '251 patent, flexible securement strips are applied in a manner similar to hanging wallpaper, wherein an adhesive is applied onto a surface within a trailer where adhesion is desired. Then a retaining strip is applied to the adhesive. In addition to this requirement of a separate adhesive, systems appearing in the past sometimes encountered problems associated with weakness at the joints. At the juncture where the strips came together, an opportunity existed for slippage of the joined panels.
In addition to the restraining system disclosed in U.S. Pat. No. 4,264,251 other systems have been developed that provide enhanced operating characteristics and advantages, as discussed in the above identified U.S. Pat. Nos. 6,089,802; 6,227,779 and 6,607,337 all of common inventorship and assignment as the subject application. The disclosures of these prior four patents, of common assignment as the subject application, are hereby incorporated by reference as though set forth at length.
Further to these prior systems of securing lading increasing attention has been placed on securing lighter loads on overland routes, without abandoning the advantages achieved by previously known commercial systems. Moreover, there is interest in facilitating placement or application and facilitating the securement function so that cargo materials can be transported with enhanced efficiency and security.
In addition, systems and procedures used in the past, which were satisfactory, and even essential, for certain demanding purposes often were more than required for securing certain loads, for example loads for land transport, where the cargo is not subject to the same level of forces as intermodal cargo containers transported by ship.
The problems suggested in the preceding are not intended to be exhaustive but rather are among many which may tend to reduce the effectiveness of cargo restraining systems known in the past. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that overland cargo-restraining systems appearing in the past will admit to worthwhile improvement.